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N2 Atmosphere (n2 + atmosphere)
Selected AbstractsSynthesis and characterization of imine-coupled polyphenols containing carbazole unitsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009smet Kaya Abstract Imine coupled phenolic monomers containing carbazole unit were synthesized in four steps. The monomers were polymerized via oxidative polycondensation by air as oxidant in an aqueous alkaline medium at 50°C. The structures of compounds were confirmed by ultraviolet,visible (UV,vis), Fourier transform infrared, and 1H- and 13C-NMR techniques. The conductivity measurements of these polymers were made by the four-point probe technique and iodine was used as doping agent. The highest occupied molecular orbital, the lowest unoccupied molecular orbital, and electrochemical and optical band gap values were calculated by the results of the UV,vis and the cyclic voltammetry measurement, respectively. The number-average molecular weight, weight-average molecular weight, and polydispersity index values were determined by the size exclusion chromatography technique. Also, thermal behavior of these polymers was determined by thermogravimetric/differential thermal analysis measurements in a N2 atmosphere between 20 and 1000°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] THE EFFECT OF MODIFIED ATMOSPHERE PACKAGING ON THE QUALITY AND SHELF LIFE OF FRANKFURTER TYPE-SAUSAGESJOURNAL OF FOOD QUALITY, Issue 2010NALAN GOKOGLU ABSTRACT The effects of modified atmosphere packaging on the quality and shelf life of frankfurter-type sausages, prepared exclusively from beef meat, were investigated. Sausages were packed under varying modified atmosphere conditions (30% CO2/70% N2; 70% CO2/30% N2; 100% CO2; 80% CO2/20% O2) and vacuum, and stored at 4C for 28 days. Lower pH values were observed in the samples packed under modified atmospheres compared to vacuum. Inhibition effect of carbon dioxide concentration on the oxidation was seen. Carbon dioxide caused microbial inhibition. The lowest total viable count was found in the samples packed under 100% CO2. It was concluded that modified atmosphere packaging had significant effect on the quality and shelf life of frankfurter-type sausages compared to vacuum packaging. The most suitable atmosphere among the tested atmospheres was that with 70% CO2, 30% N2 atmosphere. The shelf life of sausages under this atmosphere was 28 days. PRACTICAL APPLICATIONS Meat and meat products are susceptible to spoilage. Several preservation techniques are used to extend their shelf life. Packaging of fresh meat is a common application to protect its quality. Modified atmosphere packaging (MAP) means to replace the air in a package of food with some different mixture of gases. The success in MAP is to choose the suitable gas combination, packaging system, package application and the package material. Proper gas combination to keep meat quality should be provided. Several studies have been performed to extent shelf life of pork sausages and local-type sausages using modified atmosphere packaging technique. However there is no data on beef sausages. The results of this research will form the basis for further studies and also will be beneficial for industry. [source] Synthesis and bio-activity of alkyl/aryl [2-(1,2,4,5-tetrahydro-3-sulfanylene/selenylene naphtha[1,8][1,5,3]diazaphosphocin- 3-yl)methyl amino acid esters]JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 3 2010S. Subba Reddy Synthesis of alkyl/aryl [2-(1,2,4,5-tetrahydro-3-sulfanylene/selenylene naphtha[1,8- f,g][1,5,3]diazaphosphocin-3-yl) methyl amino acid esters] (6,15) was accomplished in three steps. 1, 8-diamino naphthalene (2) was reacted with tris (bromomethyl) phosphine (1) in the presence of triethylamine in dry tetrahydrofuran (THF) under N2 atmosphere to form a PIII intermediate (3). It was converted to the corresponding sulfide (4) and selenide (5) by reacting with sulfur and selenium, respectively. The intermediates 4 and 5 were further reacted with amino acid esters to obtain the title compounds (6,15). The structures of the title compounds were established by elemental analysis and spectral data (IR, 1H, 13C, 31P NMR, and FAB mass). The antimicrobial activity of these compounds was evaluated and they exhibited significant activity. J. Heterocyclic Chem., (2010). [source] Novel amorphous perfluorocopolymeric system: Copolymers of perfluoro-2-methylene-1,3-dioxolane derivativesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2006Yu Yang Abstract Perfluorotetrahydro-2-methylene-furo[3,4- d][1,3]dioxole (monomer I) and perfluoro-2-methylene-4-methoxymethyl-1,3-dioxolane (monomer II) are soluble in perfluorinated or partially fluorinated solvents and readily polymerize in solution or in bulk when initiated by a free-radical initiator, perfluorodibenzoyl peroxide. The copolymerization parameters have been determined with in situ19F NMR measurements. The copolymerization reactivity ratios are rI = 1.80 and rII = 0.80 in 1,1,2-trichlorotrifluoroethane at 41 °C and rI = 0.97 and rII = 0.85 for the bulk polymerization. These data show that this copolymerization pair has a good copolymerization tendency and yields nearly ideal random copolymers. The copolymers have only one glass-transition temperature from 101 to 168 °C, depending on the copolymer compositions. Melting endotherms have not been observed in their differential scanning calorimetry traces, and this indicates that all the copolymers with different compositions are completely amorphous. These copolymers are thermally stable (the initial decomposition temperatures are higher than 350 °C under an N2 atmosphere) and have low refractive indices and high optical transparency from UV to near-infrared. Copolymer films prepared by casting were flexible and tough. These properties make the copolymers ideal candidates as optical and electrical materials. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1613,1618, 2006 [source] Preparation and Properties of Porous Aluminum Nitride,Silicon Carbide Composite CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2004Eirik Hagen Microporous two-phase AlN,SiC composites were prepared using Al4C3 and either Si (N2 atmosphere) or Si3N4 (Ar atmosphere) as precursors. The reaction mechanisms of the two synthesis routes and the effect of processing conditions on reaction rate and the material microstructures were demonstrated. The exothermic reaction between Si and Al4C3 under N2 atmosphere was shown to be a simple processing route for the preparation of porous two-phase AlN,SiC materials. The homogeneous two-phase AlN,SiC composites had a grain size in the range of 1,5 ,m, and the porosity varied in the range of 36%,45%. The bending strength was 50,60 MPa, in accordance with the high porosity. [source] Microstructural Characterization of High-Thermal-Conductivity Aluminum Nitride CeramicJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2002Hiromi Nakano An aluminum nitride (AlN) ceramic with a thermal conductivity value of 272 W·(m·K),1, which is as high as the experimentally measured thermal conductivity of an AlN single crystal, was successfully fabricated by firing at 1900°C with a sintering aid of 1 mol% Y2O3 under a reducing N2 atmosphere for 100 h. Oxygen concentrations were determined to be 0.02 and 0.03 mass% in the grains and in the grain-boundary phases, respectively. Neither stacking fault in the grains nor crystalline phase in the grain-boundary regions was found by transmission electron microscopy. An amorphous phase possessing yttrium and oxygen elements was detected between the grains as thin films with a thickness of <1 nm. Because the amount of grain-boundary phase was small, the high-thermal conductivity of the ceramic was attributable to the low oxygen concentration in the AlN grains. [source] Preparation of ZnO thin films by MO-CVD method using bis(acetylacetonato) zinc(II) anhydrate fiberPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2010Shigeyuki Seki Abstract The MO-CVD method as a deposition process corresponding to the mass production of the high-quality ZnO film that can be used as an active layer in the thin film transistor is paid to attention. Bis(acetylacetonato) zinc(II) (Zn(acac)2) which has chemical stability and low toxicity is promising as the inexpensive raw material for CVD. The problem includes (1) pollution with water in process by character to easily take water of crystallization, and (2) the supply of the gas-phase raw material by sublimation should be not able to be controlled easily because it is a fine particle. In this study, Zn(acac)2 anhydrate fiber was prepared from Zn(acac)2 monohydrate powder by the sublimation process. Melting point of this fiber was almost same (,134 °C) as the monohydrate powder in N2 atmosphere. ZnO film was deposited on r-face sapphire substrate by MO-CVD process using Zn(acac)2 anhydrate fiber, successfully. RMS of the film flatness was 0.48 nm. This film had resistivity of 4.6 × 10,1 ,·cm, carrier electron density of 9.1 × 1017 cm,3 and Hall mobility of 15 cm2·V,1·s,1. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis of graft copolymers of xyloglucan and acrylonitrilePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 2 2008Anuradha Mishra Abstract Xyloglucan (XG), a water-soluble food grade polysaccharide is reported as a substrate for the graft copolymerization of acrylonitrile (AN). XG was extracted from tamarind seed mucilage. Polymerization was initiated both by ceric ion in aqueous medium under N2 atmosphere and with microwave (MW) irradiation. The progress of the reaction was monitored gravimetrically. The effect of different reaction parameters such as monomer concentration, level of ceric ammonium nitrate/HNO3 (CAN) initiator, reaction time and temperature, and MW power on the percent grafting (PG) was studied. Grafting of polyacrylonitrile (PAN) onto XG was confirmed by Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscope (SEM) techniques have been used to study the thermal and morphological changes in the materials. Copyright © 2007 John Wiley & Sons, Ltd. [source] The Structure-Controlling Solventless Synthesis and Optical Properties of Uniform Cu2S NanodisksCHEMISTRY - A EUROPEAN JOURNAL, Issue 35 2008Yu-Biao Chen Dr. Abstract Uniform Cu2S nanodisks have been synthesized from a well-characterized layered copper thiolate precursor by structure-controlling solventless thermolysis at 200,220,°C under a N2 atmosphere. The development from small Cu2S nanoparticles (diameter ,3,nm) to nanodisks (diameter 8.3,nm) and then to faceted nanodisks (diameter 27.5,nm, thickness 12.7,nm) is accompanied by a continuous phase transition from metastable orthorhombic to monoclinic Cu2S, the ripening of small particles by aggregation, and finally the crystallization process. The growth of the nanoproduct is constrained by the crystal structure of the precursor and the in situ-generated thiol molecules. Such controlled anisotropic growth leads to a nearly constant thickness of faceted nanodisks with different diameters, which has been confirmed by TEM observations and optical absorption measurements. [source] Absorption kinetics of oxygen scavengersINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 2 2002Gaurav Tewari The oxygen (O2) absorption kinetics of six commercial O2 scavengers were studied. The scavengers were placed in bags which were filled with 240 mL of air, 4.5 L N2 + 15 mL of air, or 3.5 L CO2 + 9 mL of air. The O2 concentration in each bag was measured at hourly intervals for 8 h. The effects of variability among individual scavengers, initial O2 concentrations of 20% or 500 ppm (0.05%), temperatures of 25, 12, 2 or ,1.5 °C, and scavenger capacity on the O2 absorption rate were determined. In addition, the effect of placing scavengers within over-wrapped trays within bags, was examined. Rates of O2 absorption varied by factors of up to 2 between individual O2 scavengers of the same type, but rates of absorption by groups of four scavengers of the same type were similar. Low temperatures gave longer O2 half-life when compared with those at higher temperatures, e.g. O2 half-lives of 7.1 and 1.0 h at ,1.5 and 25 °C, respectively, were obtained for one scavenger type. Shorter O2 half-lives were obtained in air than in N2 atmospheres at the same temperature, e.g. O2 half-lives of 1.0 and 3.3 h in air and N2 at 25 °C, respectively, were obtained for one scavenger type. The O2 absorption reactions were of first order for both high and low initial O2 concentrations. However, O2 concentration was the primary limiting factor for O2 absorption in atmospheres having O2 concentration of 500 ppm because of the dominance of diffusion. Scavengers, when placed within over-wrapped trays within bags had up to 12 times longer O2 half-lives, indicating that the O2 permeable film acts as an O2 barrier when pack atmosphere has low O2 concentrations. To obtain consistent and reproducible results, it is recommended that multiple scavengers be used in a packaging system. The appropriate number should be based on scavenger type, desired O2 absorption rate, storage temperature, and pack atmosphere (air/N2/CO2). [source] | |||||||||||||